1. Technical Field of the Invention
The present invention generally relates to the telecommunications field and, in particular, to a Base Station Subsystem (BSS) and method for handling an increase in traffic volume that overloads a terrestrial link in an Internet Protocol (IP) network.
2. Description of Related Art
The BSSs currently available for use in a wireless communications network may support both circuit switched transmissions and packet switched transmissions. The circuit switched transmissions and packet switched transmissions can be transmitted according to the Global System for Mobile Communications (GSM) standard, for example. More specifically, the packet switched transmissions can be transmitted according to the General Packet Radio Service (GPRS). And, the circuit switched transmissions can be transmitted according to the Adaptive Multi-Rate (AMR) standard.
To accommodate the increased and variable bandwidth associated with packet switched transmissions, the introduction of an IP network into the BSS has been proposed. The introduction of the IP network into the BSS referred to herein as an xe2x80x9cIP based BSSxe2x80x9d increases the flexibility and transmission efficiency of the communications network by enabling the use of statistical multiplexing. Unfortunately, not all of the Quality of Service (QoS) issues associated with mobile service are currently addressed by a network operator when dimensioning the IP based BSS.
To properly dimension the IP based BSS requires that the network operator take into account several aspects including (for example): (1) statistical behaviors of a source and service; (2) real-time requirements (e.g., sensitivity to delay and delay variations); (3) QoS issues; (4) network topology (e.g., redundant routes, trunking gains in grooming points); and (5) traffic distribution. Of course, the network operator when dimensioning the IP based BSS utilizes statistical models that include some extra margin to account for future growth. However, in view of the ever increasing demand for cellular communications the statistical models are likely to be under dimensioned, and as such may not effectively handle situations where traffic volume temporarily exceeds the initial dimensioning parameters.
During such situations, when terrestrial links in the IP network are overloaded, the current QoS priority mandates that some calls are to be disconnected in either a controlled or uncontrolled manner. However, the disconnection of any ongoing call is not acceptable to most subscribers. Accordingly, there is a need for a communications system and method capable of effectively handling a situation where an increase in traffic volume temporarily overloads the terrestrial links in the IP based BSS.
The present invention is directed to a base station subsystem (BSS) and method that effectively handles an increase in traffic volume which temporarily overloads at least one terrestrial link in an Internet Protocol (IP) network by gracefully downgrading a transmission rate of one or more calls. More specifically, the BSS preferably includes a base station transceiver (BTS), an IP gateway, and an IP network that passes at least one packet based call through a terrestrial link between the BTS and the IP gateway. The BTS and IP gateway each include an end-point having a buffer for measuring a delay in passing the at least one packet based call through the terrestrial link of the IP network and for downgrading a service when the delay as measured by one of the buffers exceeds a predetermined value.
In accordance with the present invention, there is provided a BSS and method that handles temporary overload situations within an IP domain by gracefully degrading the transmission rate of a call which, in turn, increases the robustness of a communications system.